Tool assembly

ABSTRACT

A tool assembly affording a wider range of adjustment of machining diameter, comprises a boring bar and a tool cartridge supporting a cutting tip and attached to the boring bar. The tool cartridge chassis is pivotably attached via a pin within a recess formed in boring bar; an adjustment screw is provided to a first side of the pivot axis, the screw being threaded into the cartridge chassis and situated in abutment with a surface of the bar. A compression spring is provided to a second side of the pivot axis, interposed between the boring bar and the cartridge chassis. Appreciable pivotal motion can be imparted to the cartridge chassis by loosening or tightening the adjustment screw. Adjustments can be made automatically by providing a draw-bar.

FIELD OF THE INVENTION

[0001] The present invention relates to a tool assembly comprising atool body such as a boring bar, and an adjustable machining toolcartridge attached thereto that provides improved adjustment of thecutting diameter of the tool assembly.

BACKGROUND OF THE INVENTION

[0002] A cutaway view of a conventional tool assembly is depicted inFIGS. 4 and 5. The cutting end of a boring bar 1 is illustrated, theother end of the boring bar being understood to be attached to the mainshaft of a boring machine or CNC machine via a tapered shank or thelike. Boring bar 1 is provided over an area thereof with a recess 3having a flat side wall 5 and bottom wall 7.

[0003] A tool cartridge 9 comprises a cartridge chassis 11; the chassisis fixed to boring bar 1 by means of a clamping screw 15 threaded into ascrew hole 13 formed in the boring bar. Into cartridge chassis 11 isthreaded in the axial direction an adjustment screw 17; rotation of thisscrew in the extending direction fills the space between the cartridgechassis and the end wall 6 of the recess while at the same timesupporting chassis 11 with strong force from the end wall.

[0004] Cartridge chassis 11 has a cutting tip 19 mounted thereto by aknown method. Cartridge chassis 11 is provided, in proximity to thedistal end thereof, with an adjustment screw 21 threaded into a screwhole in chassis 11, this adjustment screw being positioned so as to abutthe side walls 5 of recess 3.

[0005] With this known design, advancing adjustment screw 21 causescartridge chassis 11 to undergo elastic deformation whereby the outmostend of the cutting tip undergoes radial outward-directed displacement,allowing the machining diameter for the boring operation to be changed.

[0006] With the conventional tool cartridge 9 described above, since themachining diameter is changed via elastic deformation, the scope ofadjustment thereof is naturally limited; typically, machining diametercan be adjusted between about 0.1 and 0.4 mm, with larger toolcartridges designed for greater elastic deformation giving a range ofabout 0.5 to 0.7 mm. Accordingly, there is a need for a tool cartridgeaffording a wider range of adjustment of machining diameter in order tomeet dimensional requirements for various workpieces using an existingtool cartridge mounted on the boring bar or other similar tool.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to a tool assembly comprising atool body, for example a boring bar or the like, and a tool cartridgesupporting a cutting tip and attached to the tool body that overcomesthe limitations of the prior art and provides improved adjustment ofcutting tip edge position. This invention may be beneficially used inmills, multiple action tools, boring bars and other tools known in theart.

[0008] An object of the present invention is to provide a tool assemblycomprising a tool body, such as a boring bar, a tool cartridge having achassis and supporting a cutting tip, a pivot secured to the tool bodyfor engaging the tool cartridge, an adjustment means, and a springmeans, wherein the tool cartridge chassis is pivotably attached to thetool body, the adjustment means is positioned to a first side of thepivot and in abutment with a surface of the tool body, and the springmeans positioned on a second side of the pivot is interposed between thetool body and the chassis.

[0009] It is a further object of the invention to provide an adjustmentmeans for transmitting force to a portion of the cartridge chassis so asto impart a radial outward-directed rotational force thereto positionedon a first side of the pivot and a spring means for imparting to thecartridge chassis a rotational force in the direction opposite the firstrotational force positioned on a second side of the pivot. It is afurther object that the adjustment means and the spring means allow fineadjustment of positioning of a cutting tip on the chassis throughcontrol of the chassis' rotation about the pivot.

[0010] A further object of the present invention is to provide a boringbar wherein the chassis of the tool cartridge is pivotably attachedwithin a recess formed in the boring bar; an adjustment screw isprovided to a first side of the pivot axis, being threaded into thecartridge chassis and situated in abutment with a surface of the cuttingbar; and a tensioning device, such as a compression spring, is providedto a second side of the pivot axis, interposed between the boring barand cartridge chassis. With this design, appreciable pivotal motion canbe imparted to the cartridge chassis by loosening or tightening theadjustment screw, thereby providing a wider range of adjustment than theprior art.

[0011] Another object of the present invention is to provide a toolbody, for example a boring bar wherein the chassis of the tool cartridgeis pivotably attached within a recess formed in the boring bar and isactuated by a draw-bar. The draw-bar displaceable in the lengthwisedirection is provided to the interior of the boring bar for adjustingtool cartridge position. This draw-bar is provided, to a first side ofthe pivot axis of the cartridge chassis, with a main cam action devicefor transmitting force to a portion of the cartridge chassis so as toimpart radial outward-directed rotational force thereto; a tensioningdevice, such as a compression spring, for imparting to the cartridgechassis rotational force in the direction opposite the previousrotational force is provided to a second side of the pivot axis; and thepivoting position of the cartridge chassis is adjustable by means ofadjustment of the longitudinal position of the draw-bar in relation tothe boring bar. With this design, tool cartridge pivoting position canbe adjusted automatically over a wide range. A further object of theinvention is to provide a tensioning device, such as a compressionspring, interposed between the boring bar and cartridge chassis, thusproviding a simple design. A yet further object of the invention is fineadjustment of cartridge chassis pivoting position made via an adjustmentmeans such as a screw, cam, wedge, and the like, whether mechanical,hydraulic or pneumatic.

[0012] Alternatively, another further object of the invention is toprovide a compression spring interposed between the draw-bar and thecartridge chassis. The draw-bar includes an auxiliary cam action devicewhereby the degree of compression of the compression spring between theauxiliary cam action device and the cartridge chassis remains unchangedirrespective of the pivoting position of the cartridge chassis impartedby the main cam action device. Thus, the force produced by thecompression spring remains constant regardless of the pivoting positionof the cartridge chassis so that the degree of change in position of thecutting tip due to centrifugal force is unaffected by the pivotingposition of the cartridge chassis.

[0013] A further object of the invention is to provide a follower rodprovided between the main cam action device and the cartridge chassis;and an adjustment screw threaded into the cartridge chassis so as toabut the follower rod.

[0014] It is a yet further object of the invention to provide a boringbar wherein the recess is a groove formed coextensive with thelengthwise extension of the boring bar so as to have two side walls, andthe cartridge chassis is pivotably supported by a pin supported on thetwo side walls. This arrangement provides reliable pivotal support.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A tool assembly pertaining to a first embodiment of the inventionis depicted in FIGS. 1 and 2, and comprises a boring bar 31 and a toolcartridge 39. Boring bar 31 has a recess 33. In this embodiment, therecess takes the form of a groove with two side walls 35 for tightlyaccommodating tool cartridge 39, while allowing pivotal movement of thecartridge about a pivot axis. A pin 37 extends transversely throughrecess 33, and will be understood to be removably secured to the boringbar 31. The cartridge chassis 41 of the tool cartridge is provided witha hole through which the pin passes thereby movably attaching toolcartridge 39 to the boring bar.

[0016] Pin 37 fits the hole tightly so as to allow cartridge chassis 41to pivot about pin 37 without play. That is, the fit of pin 37 in thehole is such that movement of the chassis in relation to the pin issubstantially limited to rotation of the chassis about the pin.Cartridge chassis 41 has a curved rear edge 43 to facilitate pivotingand a distal edge 47 close to the terminal end 32 of the boring bar 31.In proximity to the distal edge 47 of cartridge chassis 41, adjustmentscrew 51 is threaded into a screw hole provided in the cartridgechassis. The distal end 52 of the adjustment screw 51 abuts a face ofthe boring bar 31. A cutting tip 49 is mounted on cartridge chassis 41by a known method analogous to that in the prior art example. The tip ismounted in a depression 40 in the cartridge chassis 41. In a furtherembodiment, the cutting edge of the cutting tip is positionedsubstantially in the center across the width of recess 33.

[0017] Towards the rear of cartridge chassis 41, boring bar 31 isprovided with a spring accommodating hole 53. A powerful compressionspring 55 is accommodated within this hole so as to press down againstthe rear section 45 of the cartridge chassis. Alternatively, the springaccommodating hole may be provided in the cartridge chassis 41. In thatcase, a plate spring or the like is preferred so as to reduce theoverall length of spring 55. Alternatively, other tensioning devicesknown in the art may be utilized. In any event, the compression springis interposed between the rear section of the cartridge chassis andboring bar 31. With the arrangement described above, when adjustmentscrew 51 is loosened, that is withdrawn along the screw hole, toolcartridge 39 is energized by compression spring 55 and pivots in theclockwise direction, as viewed in FIG. 1, from the neutral positiondepicted in FIG. 1. Whereas, when the adjustment screw 51 is tightened,that is advanced along the screw hole, it causes the tool cartridge topivot in the counterclockwise direction as viewed in FIG. 1, affordingan extremely broad range of adjustment for the cutting edge of cuttingtip 49. That is, loosening adjustment screw 51 adjusts cutting tip 49inward creating a smaller boring radius, while tightening adjustmentscrew 51 adjusts cutting tip 49 outward creating a larger boring radius.The forces produced by the strong tensioning device and the adjustmentscrew afford support adequate to withstand machining resistance over theentire range of adjustment.

[0018]FIG. 3 depicts a tool assembly according to another embodiment ofthe invention, and comprises a boring bar 61 and a tool cartridge 69.According to the present embodiment displacement of the edge of the tipis carried out automatically. For this purpose a bore 59 coextensivewith the center axis of boring bar 61 is provided, and a draw-bar 60slidable in the lengthwise direction of the boring bar is providedwithin the bore 59. The draw-bar 60 is driven by a drive unit, notshown, under the control of the control unit of the boring machine in amanner for driving draw bars that is well known in the art.

[0019] Apart from the parts described below, the arrangement of toolcartridge 69 is basically the same as that depicted in FIGS. 1 and 2, sodiscussion of the parts that are the same is omitted here and thepreceding description thereof in relation to FIGS. 1 & 2 is herebyincorporated by reference with regard to FIG. 3.

[0020] A radial hole 82 is provided in boring bar 61 at the location ofadjustment screw 81, and a follower rod 83 is slidably arranged withinthis hole. Draw-bar 60 is provided with main cam action device 84.Moving draw-bar 60 in the lengthwise direction, with reference to theboring bar, causes the tool cartridge 69 to pivot about pin 67 allowingthe radial position of the edge of the cutting tip to be changed.

[0021] A feature of the present embodiment is that the force produced bycompression spring 73 remains unchanged regardless of the pivotingposition of tool cartridge 69, thereby allowing better control ofcutting edge position. It has been established that the position of thecutting tip edge during the machining operation is determined by theoutward pushing force exerted on the adjustment screw 81 by the main camaction device 84, the force of the compression spring 73, thecentrifugal force, and force directed radially inward from theworkpiece; thus, any change in compression spring force can produce achange in cutting tip edge position. Allowing a change in spring forceproduces a change in the relationship between spring force and thetendency for tool cartridge 69 to pivot about pin 67 with centrifugalforce produced as the boring bar turns, making accurate prediction ofcutting tip edge position impossible. The problem of variable springforce is solved by means of the present embodiment wherein draw-bar 60is provided with auxiliary cam action device 85 allowing radially inwardmovement of spring 73. Alternatively, other tensioning devices known inthe art may be employed

[0022] In FIG. 3, spring 73 takes the form of a stack of a plurality ofplate springs accommodated within a spring accommodation hole 65 in toolcartridge 69. A spring retainer 89 having a follower rod 87 interposedbetween draw-bar 60 and spring 73. The profiles of the two cam actiondevices 84, 85 fulfill the following relationship.

D1:D2=L1:L2

[0023] where D1 is displacement of follower rod 83, D2 is displacementof follower rod 87 (D1 and D2 are mutually opposing directions), L1 isthe distance from the center of pin 67 to adjustment screw 81, and L2 isdistance from the center of pin 67 to of follower rod 87. Here,compression spring 73 is accommodated within tool cartridge 69, butwhere boring bar 61 has sufficient thickness, accommodation thereofwithin the boring bar is also possible.

[0024] Alternatively, compression spring 73 may be compressed betweenboring bar 61 and tool cartridge 69, as in the example depicted inFIG. 1. In this case, the force produced by the compression spring willchange, although automatic adjustment of machining diameter will beafforded.

[0025] An advantage of the preceding embodiments is the ability to makefine adjustments via the adjustment screw 81; however, automaticadjustment by the draw-bar 60 is not an essential element, it beingpossible for follower rod 83 to contact tool cartridge 69 directly.

[0026] According to the present embodiment, a portion of the mechanismfor driving the tool cartridge 69 is accommodated within the boring bar61, and as the mechanism consists simply of a draw-bar located in thecenter of the boring bar and a corresponding mechanism interposedbetween it and the tool cartridge, one or more additional elementsidentical to tool cartridge 69 or having designs based on the sameprinciple may be provided. In FIG. 3, such an additional tool cartridgeis denoted by symbol 91. While, tool cartridge 91 is showndiagrammatically, it will be readily understood that the cutting tip isarranged facing the direction of rotation of boring bar 61. It is alsopossible to provide two tool cartridges spaced apart in the diametricalor lengthwise direction or three or more thereof arranged at equidistantintervals in the circumferential direction.

[0027] By employing a plurality of tool cartridges in this way, finecutting pitch can be achieved with larger boring bar feed. The positionsof the edges of this plurality of tool cartridges can be adjusted viathe common draw bar.

[0028] According to the present embodiment, edge position can beadjusted automatically over a wide range, allowing the workpiece to berough finished to certain dimensions during the forward stroke of theboring bar and then precision finished to different dimensions duringthe return stroke. Where a plurality of tool cartridges is employed, thetool cartridge equipped with a cutting tip for precision finishmachining can be moved into the desired radial position during theprecision finish stroke. It is also possible to machine a hole tocertain dimensions during the first stroke and to then machine a largerhole partway during the second stroke. In either case, the need tore-clamp the workpiece, such as is ordinarily required when subjecting anumber of workpieces to a first operation and then again to a secondoperation, is obviated, preventing off-centering during the transitionfrom the first operation to the second operation, so as to affordprecision machining. Since there is no need to change tool cartridges,mispositioning is prevented and the need for a test operation afterattaching a new cartridge, as with conventional tool cartridges, isobviated.

[0029] In FIG. 3, the position of the cutting tip of the additional toolcartridge 91 with respect to the lengthwise extension of boring bar 61is shown as being the same as that of tool cartridge 69, but theinvention is not limited to such an arrangement. The additional toolcartridge 91 may be arranged to the rear of tool cartridge 69. In thiscase, precision finish machining can be accomplished with the cuttingtip of additional tool cartridge 91 while the cutting tip of toolcartridge 69 performs rough finish machining during the first forwardstroke of boring bar 61. In this case it is not necessary for additionaltool cartridge 91 to be identical to tool cartridge 69, and the profileof the draw-bar 60 cam action device for tool cartridge 91 can differfrom that for tool cartridge 69.

[0030] Another mechanism for adjusting the radial position of thecutting tip via the drawbar known in the art is placement of the membersupporting the cutting tip in direct contact with the cam action deviceof the draw-bar to assure that it does not undergo displacement in theradial direction, thereby completely eliminating the possibility offluctuation in machining dimension due to deformation of the compressionspring 73 employed in the present invention (as in Registered UtilityModel 25329476, for example); such a mechanism can be provided in such away that the cutting tip supported thereby is located to the rear of thecutting tips of tool cartridges 69 and 91 of the present invention, andused for precision finish machining, while using tool cartridges 69 and91 for rough finish machining exclusively. It this case, the profiles ofthe corresponding cam action devices for each cutting tip will beselected so as to allow the draw-bar to be used in common.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a sectional view of a tool assembly according to a firstembodiment of the invention taken on line 1-1 in FIG. 2.

[0032]FIG. 2 is a sectional view of the tool assembly of FIG. 1 taken online 2-2 in FIG. 1.

[0033]FIG. 3 is a sectional view of a tool assembly according to anotherembodiment of the invention showing a sectional view corresponding toFIG. 1.

[0034]FIG. 4 is a top plan view of a tool assembly showing a toolcartridge according to the prior art.

[0035]FIG. 5 is a side view of the prior art tool assembly of FIG. 4.

I claim:
 1. A tool assembly comprising a boring bar, and a toolcartridge supporting a cutting tip and attached to the boring bar, thetool cartridge comprising a chassis pivotably attached within a recessformed in the boring bar and pivotable about a pivot axis, wherein anadjustment screw is provided to a first side of the pivot axis, thescrew being threaded into the cartridge chassis and into abutment with asurface of the boring bar; and a tensioning device is provided to asecond side of the pivot axis, interposed between the boring bar andcartridge chassis.
 2. The tool assembly according to claim 1 , whereinthe recess is a groove formed coextensive with the lengthwise extensionof the boring bar so as to have two side walls.
 3. The tool assembly ofclaim 2 wherein the cartridge chassis is pivotable about a pin extendingacross the recess and secured to the two side walls.
 4. A tool assemblycomprising a boring bar and a tool cartridge supporting a cutting tipand attached to the boring bar, the tool cartridge comprising: a chassispivotably attached to the boring bar within a recess formed in theboring bar; wherein a draw-bar displaceable in the lengthwise directionis provided to the interior of the boring bar, the draw-bar beingprovided, to a first side of a pivot axis of the cartridge chassis, witha main cam action device for transmitting force to a portion of thecartridge chassis so as to impart a radial outward-directed firstrotational force thereto; and a tensioning device for imparting to thecartridge chassis a second rotational force in the direction oppositethe first rotational force provided to a second side of the pivot axis;the pivoting position of the cartridge chassis being adjustable bychanging the longitudinal position of the draw-bar.
 5. The tool assemblyaccording to claim 4 , wherein the tensioning device is providedinterposed between the boring bar and cartridge chassis.
 6. The toolassembly according to claim 4 further comprising a follower rod providedbetween the main cam action device and the cartridge chassis; and anadjustment screw threaded into the cartridge chassis so as to abut thefollower rod.
 7. The tool assembly according to claim 5 furthercomprising a follower rod provided between the main cam action deviceand the cartridge chassis; and an adjustment screw threaded into thecartridge chassis so as to abut the follower rod.
 8. The tool assemblyaccording to claim 4 , wherein the tensioning device is providedinterposed between the draw-bar and the cartridge chassis; and thedraw-bar is provided with an auxiliary cam action device whereby thedegree of compression of the tensioning device between the auxiliary camaction device and the cartridge chassis remains unchanged irrespectiveof the pivoting position of the cartridge chassis imparted by the maincam action device.
 9. The tool assembly according to claim 5 , whereinthe draw-bar is provided with an auxiliary cam action device whereby thedegree of compression of the tensioning device between the auxiliary camaction device and the cartridge chassis remains unchanged irrespectiveof the pivoting position of the cartridge chassis imparted by the maincam action device.
 10. The tool assembly according to any of claims 6,wherein the tensioning device is provided interposed between thedraw-bar and the cartridge chassis; and the draw-bar is provided with anauxiliary cam action device whereby the degree of compression of thetensioning device between the auxiliary cam action device and thecartridge chassis remains unchanged irrespective of the pivotingposition of the cartridge chassis imparted by the main cam actiondevice.
 11. The tool assembly according to claim 4 , wherein the recessis a groove formed coextensive with the lengthwise extension of theboring bar so as to have two side walls; the cartridge chassis beingpivotably supported by a pin supported on the two side walls.
 12. Thetool assembly according to claim 5 , wherein the recess is a grooveformed coextensive with the lengthwise extension of the boring bar so asto have two side walls; the cartridge chassis being pivotably supportedby a pin supported on the two side walls.
 13. The tool assemblyaccording to claim 6 , wherein the recess is a groove formed coextensivewith the lengthwise extension of the boring bar so as to have two sidewalls; the cartridge chassis being pivotably supported by a pinsupported on the two side walls.
 14. The tool assembly according toclaim 8 , wherein the recess is a groove formed coextensive with thelengthwise extension of the boring bar so as to have two side walls; thecartridge chassis being pivotably supported by a pin supported on thetwo side walls.
 15. A tool assembly comprising a boring bar, a toolcartridge having a chassis and supporting a cutting tip, a pivot securedto the boring bar for engaging the tool cartridge, an adjustment means,and a spring means, wherein the tool cartridge chassis is pivotablyattached to the boring bar, the adjustment means is positioned to afirst side of the pivot and in abutment with a surface of the boringbar, and the spring means positioned on a second side of the pivot isinterposed between the boring bar and the chassis.
 16. An adjustableboring bar comprising a recess and tool cartridge attached therein by apivot through the tool cartridge's chassis, the chassis being therebypivotably attached to the boring bar, the boring bar further comprisingan adjustment means for transmitting force to a portion of the cartridgechassis so as to impart a radial outward-directed first rotational forcethereto positioned on a first side of the pivot and a spring means forimparting to the cartridge chassis a second rotational force in thedirection opposite the first rotational force positioned on a secondside of the pivot, whereby the adjustment means and the spring meansallow fine adjustment of positioning of a cutting tip on the chassisthrough control of the chassis' rotation about the pivot.
 17. Anadjustable boring bar comprising a recess and tool cartridge attachedtherein by a pivot through the tool cartridge's chassis, the chassisbeing thereby pivotably attached to the boring bar, the boring barfurther comprising an adjustment screw positioned on a first side of thepivot and a tensioning device positioned on a second side of the pivot,whereby the adjustment screw and the tensioning device allow fineadjustment of positioning of a cutting tip on the chassis throughcontrol of the chassis' rotation about the pivot.
 18. A tool assemblycomprising a tool body, and a tool cartridge supporting a cutting tipand attached to the tool body, the tool cartridge comprising a chassispivotably attached within a recess formed in the tool body and pivotableabout a pivot axis, wherein an adjustment screw is provided to a firstside of the pivot axis, the screw being threaded into the cartridgechassis and into abutment with a surface of the tool body; and atensioning device is provided to a second side of the pivot axis,interposed between the tool body and the cartridge chassis.
 19. Anadjustable tool assembly comprising a tool body having a recess and toolcartridge attached therein by a pivot through the tool cartridge'schassis, the chassis being thereby pivotably attached to the tool body,the tool assembly further comprising an adjustment device fortransmitting force to a portion of the cartridge chassis so as to imparta radial outward-directed first rotational force thereto positioned on afirst side of the pivot and a tensioning device for imparting to thecartridge chassis a second rotational force in the direction oppositethe first rotational force positioned on a second side of the pivot,whereby the adjustment device and the tensioning device allow fineadjustment of positioning of a cutting tip on the chassis throughcontrol of the chassis' rotation about the pivot.